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aux conv
In these auxiliary power supply designs, a flyback topology is commonly used to buck link voltage to logic levels. A single switch flyback configuration is used with a DC link up to roughly 450 V, while for systems with link voltages above 500 V, a two-switch configuration is used. Silicon MOSFETs or specialized bipolar devices, such as IGBTs and ESBTs, are currently used for switching in both flyback designs. These silicon devices are limited by the die size to <1500 V. They have weak avalanche performance requiring conservative design margins, and the poor switching efficiency limits switching frequency. It is the limited performance and blocking voltage of silicon that necessitates the two-switch configuration above 500 V. In both designs, a SiC single switch flyback topology replaces the existing silicon switches. The SiC switch provides additional ruggedness with a larger voltage design margin, greater efficiency, and higher frequency over the silicon switch. Additionally, replacing the two-switch silicon topology in the high-voltage flyback with a single-switch SiC design results in a simpler topology that is easier to drive and has a lower Bill-of-Materials cost.
PTM Published on: 2013-10-30